The present invention relates generally to the field of optical shutters and switches, and particularly, pertains to optical shutters and switches which operate in the near-infrared and/or visible wavelength regions. More specifically, this invention pertains to optical shutters and switches comprising a reversible transparent-to-reflective optical shutter. This invention also pertains to methods of switching an optical signal from one input path to a selected one of a plurality of different output paths by utilizing the optical shutters and switches of this invention.
Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
As the quantity and speed of data communications over fiber optics systems rapidly increases due to the growing demand from Internet usage and other communications, improved all-optical switching systems are of increased interest to overcome the high cost and slow switching speeds of conventional switches. These conventional switches include, for example, various mechanical switches, electro-optic switches, and thermo-optic switches, such as, for example, described in U.S. Pat. Nos. 5,732,168 and 5,828,799, both to Donald. In particular, the increased complexity and cost of switching systems which involve switching from an optical signal to an electrical signal and then back to an optical signal have increased the level of interest in all-optical switches.
An all-optical switch provides switching of an optical signal from one input path to a selected one of a plurality of different output paths without any intermediate conversion of the optical signal to an electrical signal. This is typically accomplished by applying an electrical signal to a switchable element to cause the optical signal to be selectively switched. These electro-optic switches are responsive to the electrical signal to selectively switch the light of the optical signal from the input path to the selected one of the output paths.
A variety of approaches are known for making all-optical or hybrid optical switches, such as, for example, described in U.S. Pat. Nos. 5,905,587 to Maeno, et al.; 5,923,798 to Aksyuk, et al.; 5,970,185 to Baker, et al.; 5,841,912 to Mueller-Fiedler, et al.; 5,091,984 to Kobayashi, et al.; 5,406,407 to Wolff; 5,740,287 to Scalora, et al.; 5,960,133 to Tomlinson; 5,539,100 to Wasielewski et al.; and 5,943,453 to Hodgson.
The need for improved optical switches is increased by the use of wavelength multiplexing which converts the optical signal in the optical fiber into, for example, 16 signals at 16 different wavelengths in a near-infrared range of about 1540 to 1560 nm, as, for example, described in Bell Labs Technical Journal, January-March 1999, pages 207 to 229, and references therein, by Giles et al.; and in U.S. Pat. No. 5,959,749 to Danagher et al. The primary function of the optical switch is to add and/or drop optical signals from the multiple wavelengths traveling through the optical fiber. It would be highly desirable to have arrays of optical switches to handle the optical signals from multiple wavelengths per optical fiber and from multiple optical fibers, such as up to 100xc3x97100 or greater optical switch arrays. Also, it would be highly desirable if the response time for the optical switch is ultrafast, such as 1 nanosecond or less.
It would be advantageous if an all-optical switching system were available which avoided the complexity and cost of hybrid electro-optic and other switching systems while increasing the speed of the switching times from the millisecond range to the nanosecond or picosecond ranges.
One aspect of the present invention pertains to an optical shutter comprising an organic free radical compound in which the free radical compound is characterized by forming an oxidized or reduced product having a change in absorption in a near-infrared wavelength region as a result of a photo-induced electron transfer reaction of the free radical compound, wherein the change in absorption is reversible. In one embodiment, the reversible change in absorption is induced by heat. In one embodiment, the reversible change in absorption is induced by radiation selected from the group consisting of ultraviolet radiation, visible radiation, and infrared radiation; and, preferably, the reversible change in absorption is further induced by the presence of oxygen.
In one embodiment of the optical shutter of this invention, the optical shutter further comprises a metallized layer on at least one side of a photon-absorbing layer comprising the free radical compound of the optical shutter. In one embodiment, the metallized layer comprises aluminum.
Another aspect of the present invention pertains to an optical shutter comprising an organic free radical compound, preferably a radical cation compound or a radical anion compound, in which the free radical compound is characterized by forming an oxidized or a reduced product having a change in absorption in a visible and/or a near-infrared region as a result of a photo-induced electron transfer reaction of the free radical compound, wherein the change in absorption is reversible. In one embodiment, the optical shutter is utilized in an optical switch device for a fiber optics communications channel.
Still another aspect of this invention pertains to an optical shutter imageable by photons and having a first state of a low absorption and low reflection at a wavelength and a second state of a high absorption and high reflection at the wavelength, which shutter comprises a photon-absorbing layer, wherein the photon-absorbing layer comprises an organic free radical compound, as described herein, and the photon-absorbing layer is characterized by absorption of the photons by the free radical compound to form a reaction product having a change in absorption at the wavelength and by a reverse reaction of the reaction product to regenerate the free radical compound; and wherein the shutter is characterized by being reversibly imageable between the first and second states. The unique properties of the optical shutter of the present invention may be utilized to prepare a wide variety of extremely compact, picosecond speed optical devices including, but not limited to, optical switches in various arrays comprising one or more of the optical shutters.
Another aspect of the present invention relates to an optical shutter having a first state of transparency and of a low reflectivity at a range of wavelengths and a second state of opacity and of a high reflectivity at the range of wavelengths, which shutter comprises a photon-absorbing layer and a surface layer on at least one side of said photon-absorbing layer, wherein the photon-absorbing layer comprises an organic free radical compound in at least one of the first and second states and is characterized by absorption of photons to form a reaction product having a change in absorption at the range of wavelengths; and wherein the shutter is characterized by being reversibly imageable between the first and second states. In one embodiment, the optical shutter comprises a metallized layer on at least one side of said photon-absorbing layer. In one embodiment, the metallized layer comprises aluminum. In one embodiment, the absorption of photons images the shutter from the first state to the second state, and preferably, wherein the reaction product is the free radical compound. In one embodiment, the absorption of photons images the shutter from the second state to the first state, and preferably, wherein the reaction product is formed from the free radical compound. In one embodiment, absorption of photons reversibly images the shutter between the first and second state.
In one embodiment of the optical shutter of this invention, the free radical compound is a salt of an aminium radical cation. In a preferred embodiment, the free radical compound is a salt of a tetrakis[4-(dialkylamino)phenyl]-1,4-benzenediamine radical cation. In more preferred embodiment, the free radical compound is a salt of a N,N-dialkyl-Nxe2x80x2,Nxe2x80x2-bis[4-(dialkylamino)phenyl]-1,4-benzenediamine radical cation. In one embodiment, the free radical compound is a salt of an anthrasemiquinone radical anion.
In one embodiment of the optical shutter of the present invention, the wavelength range of photons imaging the shutter from the first state to the second state is different from the wavelength range of photons imaging the shutter from the second state to the first state. In one embodiment, the range of wavelengths where the change in absorption occurs is from 400 to 2000 nm.
Still another aspect of this invention pertains to an optical shutter having a first state of transparency and of low reflectivity at a range of wavelengths and a second state of opacity and of high reflectivity at the range of wavelengths, the shutter comprising a first surface layer in a transparent state, a second surface layer in a transparent state, and a photon-absorbing layer in a transparent state and interposed between the first and second surface layers, wherein the optical shutter is characterized by the absorption of photons to change at least one of the first and second surface layers to a state of high reflectivity and to change the photon-absorbing layer to a state of opacity; and wherein the shutter is characterized by being reversibly imageable between the first and second states. In one embodiment, the optical shutter is characterized by the absorption of photons to change both of the first and second surface layers to a state of high reflectivity. In one embodiment, the changes in reflectivity of the first and second surface layers occur reversibly at the same time. In one embodiment, the optical shutter comprises a metallized layer on at least one side of the photon-absorbing layer. In one embodiment, the metallized layer comprises aluminum.
In one embodiment of the optical shutter of this invention, the reversible imaging from the second state to the first state occurs with no external energy. In one embodiment, the reversible imaging from the second state to the first state is induced by heat. In one embodiment, the reversible imaging from the second state to the first state is induced by absorption of photons from one or more wavelength ranges selected from the group consisting of ultraviolet wavelength ranges, visible wavelength ranges, and infrared wavelength ranges.
Another aspect of the present invention pertains to an optical switch device comprising one or more optical input paths, two or more optical output paths, and one or more optical shutters, as described herein, the one or more shutters having a first state of transparency and of low reflectivity at a range of wavelengths and a second state of opacity and of high reflectivity at the range of wavelengths, and at least one of the one or more shutters comprises a photon-absorbing layer and a surface layer on at least one side of the photon-absorbing layer, wherein the photon-absorbing layer comprises an organic free radical compound and is characterized by absorption of photons to form a reaction product having a change in absorption at the range of wavelengths; and wherein the at least one of the one or more shutters comprising the photon-absorbing and surface layers is characterized by being reversibly imageable between the first and second states; and wherein the switch device is characterized by being capable of switching an optical signal entering the switch device from one of the one or more input paths to a selected one of the two or more output paths. In one embodiment, the switch device further comprises an optical wavelength conversion element to convert the optical signal having a first wavelength to an optical signal of a second different wavelength. In one embodiment, the optical wavelength conversion element comprises an organic free radical compound as an active material for converting the wavelength of the optical signal having the first wavelength.
Still another aspect of this invention pertains to an optical switch device comprising one or more optical input paths, two or more optical output paths, and one or more optical shutters, the one or more shutters having a first state of transparency and of low reflectivity at a range of wavelengths and a second state of opacity and of high reflectivity at the range of wavelengths, and at least one of the one or more shutters comprising a first surface layer in a transparent state, a second surface layer in a transparent state, and a photon-absorbing layer in a transparent state and interposed between the first and second surface layers, wherein the at least one of the one or more optical shutters, as described herein, that comprise the photon-absorbing and surface layers, is characterized by absorption of photons to change at least one of the first and second surface layers to a state of high reflectivity and to change the photon-absorbing layer to a state of opacity, and further is characterized by being reversibly imageable between the first and second states; and wherein the switch device is characterized by being capable of switching an optical signal entering the switch device from one of the one or more input paths to a selected one of the two or more output paths. In one embodiment, the at least one of the one or more optical shutters comprising the photon-absorbing and surface layers comprises a metallized layer on at least one side of the photon-absorbing layer. In one embodiment, the metallized layer comprises aluminum. In one embodiment, the photon-absorbing layer comprises an organic free radical compound and is characterized by an absorption of photons to form a reaction product having a change in absorption at the range of wavelengths.
In one embodiment of the optical switch device of the present invention, optical signals in the one or more input paths and the two or more output paths are bi-directional, and the switch device is characterized by the ability to switch optical signals traveling in opposite directions through the switch device. In one embodiment, the switch device comprises one or more external energy source elements to provide energy to switch the optical shutter comprising the photon-absorbing and surface layers, wherein the one or more external energy source elements are selected from the group consisting of electrical current source elements, heating source elements, ultraviolet light source elements, visible light source elements, and infrared radiation source elements. In one embodiment, the one or more external source elements are connected to an optical switch control circuit device that monitors the desired timing for providing the energy and delivers a signal to the one or more external sources of energy to provide the energy to the at least one of the one or more optical shutters comprising the photon-absorbing and surface layers.
In one embodiment of the optical switch device of this invention, the optical signal is traveling in free space in the one or more input paths and in the two or more output paths immediately prior to and immediately after the optical signal reaches the at least one of the one or more optical shutters comprising the photon-absorbing and surface layers. In one embodiment, the switch device comprises a lens in the two or more output paths to focus the optical signal. In one embodiment, the optical signal is traveling in a waveguide in the one or more input paths and in the two or more output paths immediately prior to and immediately after the optical signal reaches the at least one of the one or more optical shutters comprising the photon-absorbing and surface layers. In one embodiment, the waveguide in the two or more output paths is tapered from a larger dimension in contact to at least one of the first and second surface layers to a smaller dimension at a distance from the at least one of the first and second surface layers.
Another aspect of the present invention pertain to an optical cross-bar switch device, comprising (a) an array of optical shutters arranged in a plurality of columns and rows, each optical shutter having a first state of transparency and of low reflectivity in a range of wavelengths and a second state of opacity and of high reflectivity in the range of wavelengths, the shutter comprising a first surface layer in a transparent state, a second surface layer in a transparent state, and a photon-absorbing layer in a transparent state and interposed between the first and second layers, wherein the optical shutter is characterized by the absorption of photons to change at least one of the first and second surface layers to a state of high reflectivity and to change the photon-absorbing layer to a state of opacity; wherein the optical shutter is characterized by being reversibly imageable between the first and second states; and (b) a plurality of fiber optic ports, each fiber optic port disposed at a respective one of the columns and rows and capable of emitting and receiving a light beam so that when the light beam from a light emitting fiber optic port located at a selected one of the columns and rows is transmitted to a selected light receiving fiber optic port located at a selected remaining one of the columns and rows, the optical shutter located at an intersection formed by the selected column and row is switched to change from the non-reflective state to the reflective state to reflect the light beam from the light emitting fiber optic port to the selected light receiving fiber optic port. In one embodiment, the switch device further comprises a plurality of collimator elements, each collimator element being disposed adjacent to respective ones of each fiber optic port and between each fiber optic port and the optical shutters. In one embodiment, when the optical shutter located at the intersection formed by the selected column and row is in said second state, remaining ones of the optical shutters located in the selected column and row are in said first state. In one embodiment, a plurality of light beams from a plurality of light emitting fiber optic ports located at selected ones of the columns and rows are transmitted to a plurality of selected light receiving fiber optic ports located at selected remaining ones of the rows and columns through a plurality of optical shutters located at respective intersections formed by the selected columns and rows in the respective reflective states.
Still another aspect of this invention pertains to a method for switching an optical signal from one optical input path to a predetermined one of a plurality of different optical output paths, which method comprises the steps of (a) providing a free-space optical switch device, comprising an optical shutter disposed between an optical input path and a first and second optical output paths, the optical shutter being switchable between a transparent state in which the light from the input path is transmitted through the optical shutter to the first output path, and a reflective state in which the light from the input path is reflected from the optical shutter to the second output path; (b) inputting an optical signal into the input path; and (c) providing photons to switch the optical shutter reversibly between the transparent state and the reflective state in order to selectively direct the optical signal to a predetermined one of the output paths. In one embodiment, the optical shutter comprises a first surface layer in a transparent state, a second surface layer in a transparent state, and a photon-absorbing layer in a transparent state and interposed between the first and second surface layers, wherein the optical shutter is characterized by the absorption of photons to change at least one of the first and second surface layers to a state of high reflectivity and to change the photon-absorbing layer to a state of opacity; and wherein the optical shutter is characterized by being reversibly imageable between the first and second states. In one embodiment, the photon-absorbing layer comprises an organic free radical compound in at least one of the first and second states.
Another aspect of this invention pertains to a method for switching an optical signal from one optical input path to a predetermined one of a plurality of different optical output paths, which method comprises the steps of (a) providing a optical switch device, comprising an optical shutter disposed between an optical input port in a first input waveguide and both a first optical output port in a first waveguide and a second optical output port in a second output waveguide, the optical shutter being switchable between a transparent state in which the light from the input port is transmitted through the optical shutter to said first output port, and a reflective state in which the light from the input port is reflected from said optical shutter to said second output port; (b) inputting an optical signal into the input port; and (c) providing photons to switch the optical shutter reversibly between the transparent state and the reflective state in order to selectively direct the optical signal to a predetermined one of the output ports. In one embodiment, the optical shutter comprises a first surface layer in a transparent state, a second surface layer in a transparent state, and a photon-absorbing layer in a transparent state and interposed between the first and second surface layers, wherein the optical shutter is characterized by the absorption of photons to change at least one of the first and second surface layers to a state of high reflectivity and to change the photon-absorbing layer to a state of opacity; and wherein the optical shutter is characterized by being reversibly imageable between the first and second states. In one embodiment, the photon-absorbing layer comprises an organic free radical compound in at least one of first and second states.
Still another aspect of the present invention pertains to a method for switching an optical signal from one or more optical input paths to a predetermined one of two or more optical output paths, which method comprises the steps of (a) providing an optical switch device, as described herein; (b) inputting an optical signal into the one or more input paths; and (c) providing photons to switch the optical shutter from the first state and the second state in order to selectively direct the optical signal to a predetermined one of the two or more output paths.
As will be appreciated by one of skill in the art, features of one aspect or embodiment of the invention are also applicable to other aspects or embodiments of the invention.